MONTREAL - Everybody’s doing it. Short bouts of high-intensity exercise followed by short bouts of rest are the newest fad in fitness. Be it in CrossFit gyms or YMCAs, these condensed, hard-core exercise routines are all the rage.

The concept behind these workouts isn’t new. Interval training has been around for decades. What’s new is the format, which has been redesigned based on a couple of well-publicized studies, one out of Japan and the other out of McMaster University in Hamilton, Ont.

Before looking into the newest forms of interval training, it’s worth a look back to where it all began.

Roger Bannister, the first person to run one mile in under four minutes, is credited with initiating the first-ever interval program while training for the 1954 mile race in Vancouver. Bannister, a medical student, needed a time-efficient workout that allowed him to train over his lunch hour. He put together a 48-minute routine designed to deliver the kick necessary to bring home the mile in record time.

By current standards, a 48-minute interval workout is a little long to be considered time-efficient, yet compared to Bannister’s counterparts, who were running long, steady-state workouts each week, the express lunch hour routine was considered revolutionary.

Proponents of today’s style of interval workouts claim the same motivation as Bannister — maximum results in as short as time possible. But it’s only recently that interval workouts have been pared down to 30 minutes or less.

These abbreviated workouts, like CrossFit and the popular 7-Minute Workout, have resulted in more and more exercisers getting into the best shape of their lives in less time than they ever imagined. And they’re doing it with the backing of some pretty good science.

One of the first studies to validate the effects of short, intense interval workouts was published by Japanese exercise physiologist Izumi Tabata in 1997. Tabata analyzed the effectiveness of 20-second bouts of exercise done at 170 per cent of VO2 max (maximum aerobic power) interspersed with 10-second bouts of rest repeated six to seven times, five days a week.

Noting that Tabata’s workouts were too tough for everyone but the most fit and dedicated, Martin Gibala of McMaster tested the effects of a more moderate, but still high intensity workout. His HIT workout consisted of 10, 60-second bouts of exercise done at 90 per cent of maximum heart rate interspersed with 60 seconds of recovery.

The 20-minute workout proved not only to be time efficient, but it posted impressive improvements in fitness and health markers as well.

Using these studies as a point of reference, fitness trainers around the world have been experimenting with their own versions of Tabata and Gibala’s HIT workouts that encompass a variety of exercise modalities, including strength training, aerobic exercise and jump training (plyometrics).

The problem is, the work-to-rest ratio varies from workout to workout, which means the results are likely to vary considerably as well.

What’s the ideal bout of short intensity exercise? Well, it depends on your goals and your fitness level. The greatest improvements in fitness occur when short, very intense bouts of exercise are followed by equally short bouts of rest, similar to that tested by Tabata.

That said, Gibala’s results were also impressive, suggesting that taking it down a notch in terms of intensity and up a notch in terms of total exercise time can still be incredibly effective. Keep in mind, however, the common thread between both workouts is the principle that if you want to cut your workout time in half and still gain impressive fitness results, you need to work hard.

How hard? It’s up to you. If you’re fit, healthy and love a tough workout, try the Tabata model and see how you feel. If your fitness isn’t where you’d like it to be, but you’re still confident that you can push yourself hard, then try Gibala’s 60-seconds of hard work followed by 60-seconds rest model.

Whatever you choose, remember to introduce these tough, short workouts slowly into your regular routine. Stressing your body with high intensity workouts on back-to-back days several times a week ultimately undermines your results. To achieve the maximum benefits you need to work at the upper end of the exercise capacity, which is only possible on a well-rested body.

Start with one Tabata or HIT workout a week, slowly adding one or two workouts into your seven-day cycle, making sure that you take a day off between workouts. Keep in mind, too, that as your fitness improves (you should notice the workout getting easier in three to four weeks), you’ll need to pick up the intensity to provide the necessary stimulus to your fitter body.

Finally, you don’t need to throw out your longer, less intense workouts in favour of the Tabata or HIT exercise model.

The best results probably occur when you combine endurance workouts with shorter, more intense bouts of exercise, which allows you to build both aerobic power and endurance, arguably the best of both worlds.

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